1. Field of the Invention
This invention relates to a mobile radio terminal apparatus to be employed in a mobile communications system of cellular telephones, etc.
2. Description of the Related Art
In a mobile communications system such as a cellular telephone system, each of a number of base stations forms a cell (radio zone). Each of the cells is handled as being in a predetermined position registration area by the system. a position of the mobile radio terminal apparatus is managed in association with the position registration area to which the selected cell belongs, and outgoing and incoming calls are processed.
A conventional mobile radio terminal apparatus discriminates whether or not position registration required for standby needs to be executed, on the basis of identification information of the position registration area included in information to be notified as received from the cell selected at the standby time (refer to, for example, 3rd Generation Partnership Project (3GPP) Standards TS23.122, TS25.304). When a cell is newly selected and the position registration area to which the selected cell belongs is different from the position registration area of the previously selected cell, standby can be executed, too, in the newly selected cell, by executing the position registration.
Under the 3GPP Standards TS23.122, TS25.304), when a cell is selected and then the position registration is executed, the terminal apparatus becomes in the connection mode associated with the transmission to the cell. When the position registration is completed and the connection mode is ended, a cell is selected.
For this reason, if the cell selected by the cell selection belongs to the position registration area different from the area where the position registration has been executed, position registration is executed again immediately after the previous position registration.
This state may be caused particularly in a case where the terminal is located in an environment where a plurality of cells having different position registration areas are close to each other. For this reason, the position registration is executed at every cell selection and the battery power is wasted, in the worst case.
In the conventional mobile radio terminal apparatus, position registration is executed again in accordance with the cell selection after the position registration has been executed. The battery power is thereby wasted.